The long term objective of this study is to explain the mechanism of insulin action in the human body. The specific aim of the proposed study is to delineate the mechanism by which insulin stimulates glucose transport across the plasma membrane. This year, we plan to study the characteristics of the transport protein solubolized from fat cells and incorporated into egg lecithin liposomes. We will use the techniques established last year. We also plan to investigate whether insulin-sensitive glucose transport system is internalized by fat cells, along with the insulin-receptor complex. In addition, we will study effects of phospholipid composition on the glucose uptake by the reconstituted liposomes. It is hoped that these studies will provide basic information on the characteristics of the insulin-sensitive glucose transport mechanism.